1. Field of the Invention
The present invention relates to a simultaneous broadcasting receiver for receiving each of broadcasting signals carrying an identical broadcasting content transmitted simultaneously in different broadcasting systems.
2. Description of the Prior Art
A conventional simultaneous broadcasting receiver is such configured that a digital side is unconditionally chosen and fixed as an input system if an identical broadcasting content is broadcast simultaneously both in an analog and a digital broadcasting systems. The digital broadcasting system, in a way, has an advantage over the analog broadcasting system in its ability to prevent quality of decoded signals from easily deteriorated with the benefit of an error correcting code even if a reception status becomes poor to some extent. Because of this reason, it is reasonable to choose the digital side as the input system when the simultaneous broadcasting is received. However, the digital broadcasting system also has a disadvantage, not found in the analog broadcasting system, of producing a rapid deterioration in the quality of the decoded signals once the reception status becomes worse than a predetermined level. Due to this reason, the conventional receiver having the above-mentioned configuration in which the digital side is chosen and fixed as the input system unconditionally when the simultaneous broadcasting is received has a problem in which reproducing the audiovisual broadcast content becomes impossible unexpectedly when the reception status of the digital broadcasting signal becomes worse than the predetermined level.
As a conventional technology for solving the above-mentioned problem, the applicant of the present invention has already disclosed and proposed, for example, in Japanese Patent No. P2641148, a TV receiver comprising a decoder for performing a predetermined signal processing by receiving each of TV broadcasting signals transmitted in the digital and analog broadcasting systems, a reception status detector for detecting the reception status of the digital TV broadcasting signal, and an input system selector for selecting and feeding one of the signals processed in the decoder to a circuit following thereto according to the detection result of the reception status detector.
The TV receiver configured in such a way as described above, when the reception status of the digital broadcasting signal is deteriorated, the input system can be switched over from the analog side to the digital side temporarily before a rapid deterioration in the quality of the decoded signal further develops. Accordingly, in a way, it is possible to output video images and sounds in such a quality level by which the broadcasting content is understood on the whole.
However, because the TV receiver configured in such a way as described above keeps feeding power to the decoder of the analog side regardless of the reception status of the digital TV broadcasting signal, the TV receiver has a problem in which the power fed to and consumed by the decoder of the analog side is wasted when the reception status of the digital TV broadcasting signal is good. Because the TV receiver configured in a way as described above has no compensation means for compensating for a loss of synchronization of output timing that is caused when the input system is selected, the TV receiver also has a problem in which the audio signal or the video signal is interrupted every time the input system is switched over.